1. Field of the Invention
This invention generally relates to a thin film deposition apparatus and more particluarly to the improvement of a microwave plasma film deposition system for depostion of a thin film by using electron cyclotron resonance (hereunder abbreviated as ECR) plasma.
2. Description of the Related Art
As an example of a conventional metal thin film deposition apparatus using microvwave, Japanese Patent Application Provisional Publication No. 59-47728 discloses a plasma thin film deposition apparatus including a plasma cavity, in which plasma is generated, and a specimen chamber for accommodating a specimen and further including a plasma extraction window having a target provided therebetween, whereby gas can be supplied to both the plasma cavity and the specimen chamber. This conventional apparatus can effect low-temperature thin film deposition, which is an advantage of ECR plasma thin film deposition method, and can deposit a thin film of good quality with the extent of the strength of depositing thereof being large.
FIG. 1 is a diagram for showing the construction of the above described plasma thin film depostion apparatus. In this figure, reference numeral 1 designates a plasma cavity; 2 a specimen chamber; and 3 a microwave feeding window using a quartz glass. Microwave is supplied from a rectangular waveguide 4 through the microwave feeding window 3 to the plasma cavity 1. Further, in the plasma cavity 1, a plasma extraction window 5 is provided in such a manner to face the microwave feeding window 3, and the plasma is introduced onto a specimen rest on which a specimen substrate 7 is arranged . The specimen chamber 2 is connected to an evacuation system 9. A magnetic coil 10 is provided around the periphery of the plasma cavity 1 and the magnitude of the magnetic field produced by the magnetic coil 10 is arranged such that the conditions required for occurring ECR in case of microwave are satisified in a part of the plasma cavity 1. Further, this conventional apparatus is provided with two gas supplying systems, that is, a first gas supplying system 12 for supplying gas used for generating plasma to the plasma cavity 1 and a second gas supplying system 13 for supplying feed gas to the specimen chamber 2. Moreover, the plasma cavity 1 is refrigerated by letting refrigerant run through pipes 13 thru 15. Furthermore, a target electrode 17 containing sputtering material 16 is arranged in such a manner to surround a plasma flow and is connected to a power source 19 for sputtering.
Indeed, this metal thin film deposition apparatus making use of the ECR plasma and the sputtering technique takes the advantage of the ECR plasma. However, in the case where the thin film is conductive, particles of metallic atoms sputtered from a sputtering target are diffused in the plasma cavity 1 and then the deposition of the metal thin film on the surface of the microwave feeding window 3 occurs and prevents the propagation of the microwave so that it becomes impossible to stably discharge and thus the deposition of the thin film cannot be continued. Thus, this conventional apparatus has a drawback that the deposition of the thin film cannot be effected with good reproductiveness.
Incidentally, by this apparatus, the deposition of the thin film can be effected by using chemical vapor depostion (hereunder abbreviated as CVD) method. Moreover, in theory, the deposition of a metal thin film can be effected by this apparatus on condition that a discharge gas (for example, hydrogen gas) is issued from the first gas supplying system 12 and on the other hand an organometallic gas (for instance, tri-methyl aluminum (TMA) gas and WF.sub.6 gas) is issued from the second gas supplying system 13. However, the deposition of the metal thin film cannot be stably effected by this conventional apparatus for the same reason as above described with relation to the case of the deposition of the conductive thin film.
This invention is accomplished to eliminate the drawbacks of the conventional apparatus above described.